Method of expressing long-chain prenyl diphosphate synthase

ABSTRACT

The present disclosure describes a method of producing a long-chain prenyl diphosphate synthase (in particular decaprenyl diphosphate synthase and solanesyl diphosphate synthase) using a gene and a protein which are required for enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase as well as a method of efficiently producing a coenzyme Q having a long-chain isoprenoid in its side chain (in particular coenzyme Q 9  or coenzyme Q 10 ) using a microorganism. The present disclosure also describes a DNA having a base sequence shown under SEQ ID NO:1, 3 or 5 and a DNA sequence derived from the above base sequence by deletion, addition, insertion and/or substitution of one to several bases thereof, and coding for a protein enabling (functioning) or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a cell of a host organism.

This application is a divisional application of U.S. patent application Ser. No. 10/477,269 filed Mar. 19, 2004, now U.S. Pat. No. 7,402,413 which is §371 filing based on PCT/JP2002/04566, filed May 10, 2002, and claims priority to the Japanese Patent Application No. 2001-140977 filed on May 11, 2001. The disclosure of each of these applications is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a protein involved in the expression of a eukaryotes-derived long-chain prenyl diphosphate synthase, a gene coding for such enzyme, a vector containing such enzyme gene, a transformant resulting from transformation with such vector and a long-chain prenyl diphosphate synthase gene-containing expression vector as well as a method of producing a long-chain prenyl diphosphate synthase (in particular decaprenyl diphosphate synthase and solanesyl diphosphate synthase) and of a coenzyme Q having a long-chain isoprenoid in its side chain (in particular coenzyme Q₉ or coenzyme Q₁₀).

BACKGROUND ART

“Isoprenoids” is a generic name for a variety of compounds, including sterols, carotinoids and terpenes, among others. Among them, there is a group of prenyl diphosphate compounds containing a coenzyme Q side chain, and the synthesis thereof depends on the polymerization-like condensation reaction of isopentenyl diphosphate, which is an isoprene unit containing 5 carbon atoms, as catalyzed by a prenyl diphosphate synthase.

The respective prenyl diphosphate synthases are roughly classified into 4 groups.

The short chain (3 or 4 isoprene units) prenyl diphosphate synthases are known to perform their catalytic function in the form of homodimers. Examples of such are farnesyl diphosphate synthase (Eberthardt, N. L. (1975), J. Biol. Chem., 250, 863-866) and geranylgeranyl diphosphate synthase (Sagami, H. (1994), J. Biol. Chem., 269, 20561-20566).

The medium chain (6 or 7 isoprene units) prenyl diphosphate syntheses are known to be heterodimeric enzymes composed of two proteins each independently having no catalytic activity. Examples are hexaprenyl diphosphate synthase (Fujii, H. (1982), J. Biol. Chem., 257, 14610), and heptaprenyl diphosphate synthase (Takahashi, I. (1980), J. Biol. Chem., 255, 4539).

Further, as for the long-chain (8 to 10 isoprene units) prenyl diphosphate syntheses, it is reported that prokaryote-derived such enzymes are undissociable homodimers and are activated by a polyprenyl diphosphate carrier protein (Ohnuma, S. (1991), J. Biol. Chem., 266, 23706-23713). At present, however, there is no report available about eukaryotes-derived long-chain prenyl diphosphate syntheses.

Coenzymes Q are composed of a quinone skeleton and an isoprenoid side chain and occur widely in a variety of living things, from microorganisms, such as bacteria and yeasts, to higher animals and plants. In prokaryotes, they occur in the plasma membrane and function as electron acceptors for cell membrane stabilization and for periplasmic membrane protein disulfide bond formation. In eukaryotes, they occur in the mitochondrial membrane and/or cytoplasmic membrane, and serve as essential factors in the electron transfer system in the mitochondrial respiratory chain and in the oxidative phosphorylation, function as antioxidants and contribute to the stabilization of biomembranes.

Coenzymes Q having an isoprenoid side chain resulting from condensation of 8 to 10 isoprene units, among others, have attracted attention as materials of health foods and the like. Among them, coenzyme Q₁₀ comprising 10 isoprene units is intrinsic in humans and is therefore very useful and is in use as a heart medicine.

Commercially, this coenzyme Q₁₀ is produced, for example, by isolating coenzymes Q from a plant, such as tobacco, and synthetically modifying the side chain length thereof.

It is also known that coenzyme Q₁₀ is produced by a wide variety of organisms, from microorganisms, such as bacteria and yeasts, to higher animals and plants, and the method comprising cultivating a microorganism and extracting this substance from cells thereof is thought to be one of the most efficient methods of production thereof and, actually, is in use in commercial production thereof. However, such methods cannot be said to be satisfactory in productivity since, for example, the yield is poor and/or the procedure is complicated.

Attempts have also been made to isolate genes involved in biosynthesis of coenzyme Q₁₀, amplify the genes by means of the recombinant DNA technology and utilizing them in increasing the production of coenzyme Q₁₀. In living organisms, coenzyme Q₁₀ is produced via a multistage complicated reaction process in which a number of enzymes are involved. The biosynthetic pathway therefor in prokaryotes differs in part from that in eukaryotes. Basically, however, the pathway comprises three main steps, namely the step of the synthesis of decaprenyl diphosphate to serve as the source of the decaprenyl side chain of coenzyme Q₁₀, the step of the synthesis of parahydroxybenzoic acid to serve as the source of the quinone ring, and the step of the coupling of these two compounds, followed by successive substituent conversion to complete coenzyme Q₁₀. Among the reactions involved, the reactions involved in decaprenyl diphosphate synthase, which are said to determine the rate of the whole biosynthetic reaction process and which determine the length of the side chain of coenzyme Q₁₀, are considered to be the most important reactions.

For efficient production of coenzyme Q₁₀, it is considered effective to isolate the decaprenyl diphosphate synthase gene, which is the key gene in the biosynthesis in question, and utilize the same for causing a production increase. Thus, so far, decaprenyl diphosphate synthase genes have been isolated from several microbial species, such as Schizosaccharomyces pombe (JP-A-09-173076) and Gluconobacter suboxydans (JP-A-10-57072) and studied for their use in coenzyme Q₁₀ production. As for the host microorganism for this coenzyme Q₁₀ production, it is desirable to use prokaryotes, such as Escherichia coli, from the viewpoint of productivity, safety, recombinant system preparation, and so on.

As for the decaprenyl diphosphate synthase gene sources, it is also possible to utilize eukaryotes in which coenzyme Q₁₀ is produced in relatively large amounts. Thus, for example, fungi are strong candidates. However, when a eukaryote-derived decaprenyl diphosphate synthase gene was introduced by recombination into those microorganisms which belong to the prokaryotes, for example Escherichia coli, coenzyme Q₁₀ was not produced or was produced only in unsatisfactory amounts. It is thought that this is due to an insufficient level of expression of the long-chain prenyl diphosphate synthase. Therefore, the development of a method of causing efficient expression, in prokaryotes, of a eukaryote-derived decaprenyl diphosphate synthase gene serving in relatively abundant coenzyme Q₁₀ production has been desired.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a protein involved in the expression of a eukaryotes-derived long-chain prenyl diphosphate synthase, a gene coding for such enzyme, a vector containing such enzyme gene, a transformant resulting from transformation with such vector and a long-chain prenyl diphosphate synthase gene-containing expression vector as well as a method of producing a long-chain prenyl diphosphate synthase (in particular decaprenyl diphosphate synthase and solanesyl diphosphate synthase) and of a coenzyme Q having a long-chain isoprenoid in its side chain (in particular coenzyme Q₉ or coenzyme Q₁₀).

Presupposing that, in the group of long-chain prenyl diphosphate synthase-biosynthesizing eukaryotes, there might be two forms of prenyl diphosphate synthase, the present inventors considered that when derived from the genus Saitoella or the like, the enzyme of which recombinant gene expression in Escherichia coli, a prokaryote, had been confirmed would be expressed in the homo form and that when derived from the genus Schizosaccharomyces or the like, the enzyme of which recombinant gene expression in Escherichia coli could not be confirmed would be expressed in the hetero form. Thus, they considered that there might be another gene involved in the expression of such a long-chain prenyl diphosphate synthase gene incapable of being expressed upon gene recombination and the long-chain prenyl diphosphate synthase gene would be expressed with the cooperation of the other gene and that, therefore, transformation of a prokaryotic host, such as Escherichia coli, with the long-chain prenyl diphosphate synthase gene alone could not result in satisfactory activity production.

Accordingly, they made investigations in an attempt to isolate a gene involved in the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase gene and succeeded in isolating genes enhancing the expression, in Escherichia coli, of the eukaryote-derived long-chain prenyl diphosphate synthase gene from a microorganism belonging to the genus Schizosaccharomyces and the higher animals mouse and human. Thus, they have now completed the present invention.

The present invention thus relates to a DNA defined below under (a), (b) or (c):

(a) a DNA having a base sequence shown under SEQ ID NO:1, 3 or 5 and coding for a protein enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism;

(b) a DNA having a base sequence derived from the base sequence shown under SEQ ID NO:1, 3 or 5 by deletion, addition, insertion and/or substitution of one to several bases thereof and coding for a protein enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism; (c) a DNA capable of hybridizing with a DNA comprising the base sequence shown under SEQ ID NO:1, 3 or 5 under a stringent condition and coding for a protein enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism.

The invention also relates to a protein defined below under (d) or (e):

(d) a protein having an amino acid sequence shown under SEQ ID NO:2, 4 or 6 and enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism;

(e) a protein having an amino acid sequence derived from the amino acid sequence shown under SEQ ID NO:2, 4 or 6 by deletion, addition, insertion and/or substitution of one to several amino acid residues and enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism.

The invention further relates to a DNA coding for the protein defined above under (d) or (e).

Further, the invention relates to an expression vector resulting from insertion of the above DNA into a vector for expression; the expression vector as defined above wherein the vector for expression is pSTV28; the expression vector as defined above which is pSTVDLP1; the expression vector as defined above which is pSTVK28-mDLP1; and the expression vector as defined above which is pSTVK28-hDLP1.

Furthermore, the invention relates to a transformant resulting from transformation of a host microorganism with the above DNA; a transformant resulting from transformation of a host microorganism with the above expression vector; the transformant as defined above wherein the host microorganism is Escherichia coli; the transformant as defined above which is E. coli DH5α(pSTVDLP1) (FERM BP-7433); the transformant as defined above which is E. coli DH5α(pSTVK28-mDLP1); and the transformant as defined above which is E. coli DH5α(pSTVK28-hDLP1).

The invention further relates to the transformant as defined above which harbors a eukaryote-derived long-chain prenyl diphosphate synthase gene further introduced therein; the transformant as defined above wherein the eukaryote-derived prenyl diphosphate synthase gene is a gene derived from a microorganism belong to the genus Schizosaccharomyces, Saitoella, Rhodotorula, Leucosporidium, Aspergillus or Bulleomryces, a human-derived gene or a mouse-derived gene; the transformant as defined above which is E. coli DH5α(pSTVDLP1, pBSDPS) (FERM BP-7548); the transformant as defined above which is E. coli DH5α(pSTVDLP1, pUhDPS1) (FERM BP-8025); the transformant as defined above which is E. coli DH5α(pSTVDLP1, pBmSDS1); the transformant as defined above which is E. coli DH5α(pSTVK28-mDLP1, pUhDPS1); the transformant as defined above which is E. coli DH5α(pSTVK28-mDLP1, pBmSDS1) (FERM BP-8027); the transformant as defined above which is E. coli DH5α(pSTVK28-hDLP1, pUhDPS1) (FERM BP-8026); or the transformant as defined above which is E. coli DH5α(pSTVK28-hDLP1, pBmSDS1).

Still further, the invention relates to a method of producing coenzymes Q which comprises cultivating the transformant as defined above in a medium to cause formation and accumulation of a coenzyme Q in the culture and recovering the same.

DETAILED DISCLOSURE OF THE INVENTION

In the following, the present invention is described in detail.

The DNAs of the invention were isolated as follows.

Using the sequence of the decaprenyl diphosphate synthase gene of the genus Schizosaccharomyces, a homology search was conducted from a chromosomal database for the genus Schizosaccharomyces, and gene relatively high in homology was found out. Based on the above-mentioned gene sequence, genes relatively high in homology were also found out from chromosomal databases for the mouse and human, respectively.

For separating the thus-found gene from the chromosome of the genus Schizosaccharomyces, PCR primers, N-dlp1 (SEQ ID NO:7) and C-dlp1 (SEQ ID NO:8) were synthesized. For the separation from the human chromosome, hDLP1-N (SEQ ID NO:9) and hDLP1-C (SEQ ID NO:10) were synthesized and, for the separation from the murine chromosome, mDLP1-N (SEQ ID NO:11) and mDLP1-C (SEQ ID NO:12) were synthesized.

Using these primers, the PCR conditions were studied and determined, and PCR was carried out by 2 minutes of heat treatment at 94° C. and 25 repetitions of the cycle one minute at 94° C.→one minute at 56° C.→two minutes at 72° C. That a DNA of about 900 bp was amplified from the chromosomal gene of Schizosaccharomyces pombe IFO 1628, a DNA about 1,200 bp from the human chromosome, and a DNA about 1,200 bp from the murine chromosome was revealed by analyzing the base sequences of the respective genes. The DNAs obtained were sequenced and found to have the base sequences shown in the sequence listing under SEQ ID NO:1, 3, and 5, respectively.

The DNA of the present invention, which is a DNA coding for a protein enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism, may be a DNA having the base sequence shown under SEQ ID NO:1, 3 or 5, or a DNA having a base sequence derived from the base sequence shown under SEQ ID NO:1, 3 or 5 by deletion, addition, insertion and/or substitution of one to several bases, or a DNA capable of hybridizing with the DNA comprising the base sequence shown under SEQ ID NO:1, 3 or 5 under a stringent condition.

Since a number of amino acids are encoded by one or more codons (genetic code degeneracy), not only the DNA comprising the base sequence shown under SEQ ID NO:1, 3 or 5 but also a number of other DNAs code for a protein comprising the amino acid sequence shown under SEQ ID NO:2, 4 or 6. Therefore, the DNA of the invention includes those DNAs coding for a protein comprising the amino acid sequence shown under SEQ ID NO:2, 4 or 6.

The term “base sequence derived from a base sequence by deletion, addition, insertion and/or substitution of one to several bases” as used herein means a base sequence resulting from deletion, addition, insertion and/or substitution of such a number of bases as can be deleted, added, inserted and/or substituted by a method well known to those skilled in the art as described in Supplemental Issue, Tanpakushitsu, Kakusan, Koso (Protein, Nucleic Acid and Enzyme), PCR Method for Gene Amplification, TAKKAJ, 35 (17), 2951-3178 (1990) or Henry A. Erlich (ed.), translated into Japanese under the supervision of Ikunoshin Kato: PCR Technology (1990), for instance.

The term “DNA capable of hybridizing with a DNA comprising the base sequence shown under SEQ ID NO:1, 3 or 5 under a stringent condition” means a DNA obtained by the colony hybridization, plaque hybridization or Southern hybridization technique, among others, using, as a probe, the DNA comprising the base sequence shown under SEQ ID NO:1, 3 or 5. Those skilled in the art can easily obtain any desired DNA by conducting such hybridization according to the method described in Molecular Cloning, 2nd Edt. (Cold Spring Harbor Laboratory Press, 1989). For example, the desired DNA can be obtained by carrying out the hybridization at a temperature of not lower than 50° C. in urea-free SSC having a salt concentration of not higher than 0.5 M.

Further, the term “protein enabling or enhancing the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism” indicates a protein that increases the coenzyme Q production in the host microorganism by causing a eukaryote-derived long-chain prenyl diphosphate synthase gene to be expressed in the host microorganism harboring the gene as introduced therein and thus enabling or enhancing the expression of the long-chain prenyl diphosphate synthase activity.

Whether a protein is such a protein or not can be checked by preparing a transformant resulting from transformation with the long-chain prenyl diphosphate synthase gene alone and a transformant resulting from transformation with the long-chain prenyl diphosphate synthase gene together with a DNA coding for the protein in question and measuring and comparing the coenzyme Q productions in both transformants under the same conditions. In other words, when the coenzyme Q production is absolutely zero or little in the transformant resulting from transformation with the long-chain prenyl diphosphate synthase gene alone but the coenzyme Q production is significant in the transformant resulting from transformation with the long-chain prenyl diphosphate synthase gene together with the DNA coding for the protein in question, the protein corresponds to the one defined hereinabove.

The protein of the invention, which is a protein enabling or enhancing (potentiating) the activity expression of a eukaryote-derived long-chain prenyl diphosphate synthase in a host microorganism, may be a protein having the amino acid sequence shown under SEQ ID NO:2, 4, or 6, or a protein having an amino acid sequence derived from the amino acid sequence shown under SEQ ID NO:2, 4 or 6 by deletion, addition, insertion and/or substitution of one to several amino acid residues.

The “amino acid sequence derived by deletion, addition, insertion and/or substitution of one to several amino acid residues” so referred to herein can be obtained by deleting, adding, inserting and/or substituting such a number of amino acid residues as can be deleted, added, inserted and/or substituted by a method well known to those skilled in the art, for example by the technique of site-specific mutagenesis. Such method is more specifically described in the literature, for example Nucleic Acids Res., 10, 6487 (1982), and Methods in Enzymology, 100, 448 (1983).

For causing the protein of the invention to be expressed, it is necessary to join the gene for the protein to the downstream of an appropriate promoter. For example, an expression vector can be prepared by excising a DNA fragment containing the gene with restriction enzyme treatment, or amplifying, by PCR, the enzyme-encoding gene segment alone, and inserting this into a promoter-containing vector for expression.

The expression vector of the invention comprises a vector for expression with the above-mentioned DNA inserted therein.

The vector for expression is not particularly restricted but may be, for example, one resulting from insertion of an appropriate promoter into an Escherichia coli-derived plasmid. As the Escherichia coli-derived plasmid, there may be mentioned, for example, pSTV28, pBR322, pBR325, pUC19, and pUC119. As the promoter, there may be mentioned, for example, the T7 promoter, trp promoter, tac promoter, lac promoter, and λPL promoter.

In the practice of the invention, pGEX-2T, pGEX-3T, pGEX-3× (the three being products of Pharmacia), pBluescript II, pUC19 (product of Toyobo), pMALC2, pET-3T, pUCNT (described in WO 94/03613) and the like may also be used as the vector for expression.

Among them, pSTV28 is suitably used. In specific examples, an expression vector designated as pSTVDLP1 can be constructed by inserting a DNA comprising the base sequence shown under SEQ ID NO:1 into the vector pSTV28 for expression, an expression vector designated as pSTVK28-hDLP1 by inserting a DNA comprising the base sequence shown under SE ID NO:3 into pSTV28, and an expression vector designated as pSTVK28-mDLP1 by inserting a DNA comprising the base sequence shown under SEQ ID NO:5 into pSTV28.

The transformant of the invention may be one resulting from transformation of a host microorganism with the DNA mentioned above, or one resulting from transformation of a host microorganism with the expression vector mentioned above, or one resulting from transformation of a host microorganism with the above-mentioned DNA or expression vector together with a eukaryote-derived long-chain prenyl diphosphate synthase gene used additionally.

By introducing the above expression vector, together with an expression vector containing a eukaryote-derived long-chain prenyl diphosphate synthase gene, into an appropriate host microorganism, it becomes possible to utilize the resulting transformant in coenzyme Q production.

The eukaryote to serve as the long-chain prenyl diphosphate synthase gene source is not particularly restricted but includes, among others, decaprenyl diphosphate synthase-producing microorganisms belonging to the genera Schizosaccharomyces, Saitoella, Rhodotorula, Leucosporidium, Aspergillus, Bulleomyces and the like, human beings, and solanesyl diphosphate synthase-producing mice.

The host microorganism is not particularly restricted. Escherichia coli and the like are suitably used, however. The species of Escherichia coli is not particularly restricted but includes XL1-Blue, BL-21, JM109, NM522, DH5α, HB101, and DH5, among others. Among them, Escherichia coli DH5α is suitably used.

When, for example, the above-mentioned expression vector pSTVDLP1 is introduced, together with an expression vector for the decaprenyl diphosphate synthase gene derived from the genus Schizosaccharomyces, into Escherichia coli, the microorganism can be converted into a transformant capable of producing significant amounts of coenzyme Q₁₀ which originally cannot be produced in Escherichia coli.

The transformant of the invention includes, among others, the following:

The E. coli strain DH5α(pSTVDLP1) resulting from transformation with pSTVDLP1;

The E. coli strain DH5α(pSTVK28-mDLP1) resulting from transformation with pSTVK28-mDLP1;

The E. coli strain DH5α(pSTVK28-hDLP1) resulting from transformation with pSTVK28-hDLP1;

The E. coli strain DH5α(pSTVDLP1, pBSDPS) resulting from transformation with pSTVDLP1 and pBSDPS;

The E. coli strain DH5α(pSTVDLP1, pUhDPS1) resulting from transformation with pSTVDLP1 and pUhDPS1;

The E. coli strain DH5α(pSTVDLP1, pBmSDS1) resulting from transformation with pSTVDLP1 and pBmSDS1;

The E. coli strain DH5α(pSTVK28-mDLP1, pUhDPS1) resulting from transformation with pSTVK28-mDLP1 and pUhDPS1;

The E. coli strain DH5α(pSTVK28-mDLP1, pBmSDS1) resulting from transformation with pSTVK28-mDLP1 and pBmSDS1;

The E. coli strain DH5α(pSTVK28-hDLP1, pUhDPS1) resulting from transformation with pSTVK28-hDLP1 and pUhDPS1; and

The E. coli strain DH5α(pSTVK28-hDLP1, pBmSDS1) resulting from transformation with pSTVK28-hDLP1 and pBmSDS1.

Among them, E. coli DH5α(pSTVDLP1) has been deposited with the National Institute of Advanced Industrial Science and Technology International Patent Organism Depositary, Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan as of Jan. 18, 2001 under the accession number FERM BP-7433,

E. coli DH5α(pSTVDLP1, pBSDPS) as of Apr. 17, 2001 under the accession number FERM BP-7548,

E. coli DH5α(pSTVDLP1, pUhDPS1) as of Apr. 19, 2002 under the accession number FERM BP-8025,

E. coli DH5α(pSTVK28-mDLP1, pBmSDS1) as of Apr. 19, 2002 under the accession number FERM BP-8027, and

E. coli DH5α(pSTVK28-hDLP1, pUhDPS1) as of Apr. 19, 2002 under the accession number FERM BP-8026.

By using the DNA of the invention combinedly with a eukaryote-derived long-chain prenyl diphosphate synthase gene expression vector and, in addition, introducing another gene involved in the biosynthesis of a coenzyme Q simultaneously into the microorganism employed, it becomes possible to expect a still better result.

As the other gene, there may be mentioned, for example, the polyprenyl diphosphate transferase gene and the like.

A coenzyme Q can be produced in the conventional manner by cultivating the transformant obtained in accordance with the invention in a medium and recovering the coenzyme Q form the culture.

In cases where the host microorganism is Escherichia coli, LB medium, M9 medium containing glucose and/or casamino acids, and the like can be used as the medium. For efficient promoter functioning, such an agent as isopropylthiogalactoside and/or indolyl-3-acrylic acid, for instance, may be added to the medium. The cultivation is carried out, for example, at 20 to 40° C., preferably at 30 to 37° C., more preferably at 37° C., for 17 to 24 hours and, on that occasion, aeration, agitation and the like may be made according to need.

In the practice of the invention, the coenzyme Q obtained may be optionally purified or used in the form of a roughly purified product according to the intended use thereof.

For coenzyme Q purification from the culture obtained, an appropriate combination of separation/purification methods known in the art can be used. As the separation/purification methods known in the art, there may be mentioned the methods utilizing the difference in electric charge, such as ion exchange chromatography, the methods utilizing the difference in specific affinity, such as affinity chromatography, and the methods utilizing the difference in hydrophobicity, such as reversed phase high-performance liquid chromatography, among others.

The use of the coenzyme Q obtained in accordance with the invention is not particularly restricted but the coenzyme Q can be suitably used in drugs, foods and so forth.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a restriction enzyme map of the expression vector pSTVDLP1.

FIG. 2 is a restriction enzyme map of the expression vector pSTVK28-hDLP1.

FIG. 3 is a restriction enzyme map of the expression vector pSTVK28-mDLP1.

FIG. 4 to FIG. 8 show HPLC analysis charts for the products formed by a host and transformants thereof.

BEST MODES FOR CARRYING OUT THE INVENTION

The following examples illustrate the present invention in further detail. These examples are, however, by no means limitative of the scope of the invention.

Example 1

Using the base sequence of the decaprenyl diphosphate synthase gene of Schizosaccharomyces pombe, homology search was conducted in the Sanger Center database and, as a result, a gene having 26% homology was found out by means of GENETYX (Software Development Co., Ltd.). PCR primers, N-dlp1 (SEQ ID NO:7) and C-dlp1 (SEQ ID NO:8), were prepared for obtaining that gene. Separately, the chromosomal DNA of Schizosaccharomyces pombe IFO 1628 was prepared by the method of C. S. Hoffman et al. (Gene, 57 (1987), 267-272). Using these, PCR was carried out by 2 minutes of heat treatment at 94° C. followed by 25 repetitions of the following cycle: one minute at 94° C.→one minute at 56° C.→two minutes at 72° C. The thus-amplified DNA was analyzed by 0.7% agarose gel electrophoresis.

The thus-obtained fragment of about 900 bp was excised from the gel, purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech) and then cloned in a vector for expression in Escherichia coli using a PCR product direct cloning kit (pT7BlueT-Vector Kit, product of NOVAGEN) to give pT7-DLP1. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, the full-length sequence occurring on the database could be obtained.

pT7-DLP1 was cleaved with the restriction enzymes EcoRI and EcoRV (products of Takara Shuzo), followed by 0.8% agarose gel electrophoresis. The fragment of about 900 bp was excised from the gel and purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech), and this DNA fragment was then inserted into pSTV28 (product of Takara Shuzo) at the EcoRI-SmaI site. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, an expression vector, pSTVDLP1, could be obtained. A restriction enzyme map of the expression vector pSTVDLP1 is shown in FIG. 1.

The E. coli DH5α(pSTVDLP1) strain obtained by transformation with the above-obtained pSTVDLP1 has been deposited with the National Institute of Advanced Industrial Science and Technology International Patent Organism Depositary, Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan as of Jan. 18, 2001 under the accession number FERM BP-7433.

Example 2

Using the base sequence of the DLP1 gene of Schizosaccharomyces pombe as obtained in Example 1, homology search was conducted in a Genbank database and, as a result, a gene having 27% homology was found out by means of GENETYX (Software Development Co., Ltd.). PCR primers, hDLP1-N (SEQ ID NO:9) and hDLP1-C (SEQ ID NO:10), were prepared for obtaining that gene. Using a human liver cDNA library (cDNA Library, Human Liver, plasmid type (product of Takara Shuzo)) as a template, PCR was carried out by 2 minutes of heat treatment at 94° C. followed by 35 repetitions of the following cycle: one minute at 94° C.→one minute at 56° C.→two minutes at 72° C. The thus-amplified DNA was analyzed by 0.7% agarose gel electrophoresis.

The thus-obtained fragment of about 1,200 bp was excised from the gel, purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech) and then cloned in a vector for expression in Escherichia coli using a PCR product direct cloning kit (pT7BlueT-Vector Kit, product of NOVAGEN) to give pT7-hDLP1. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, the full-length sequence occurring on the database could be obtained.

pT7-hDLP1 was cleaved with the restriction enzymes BamHI and HindIII (products of Takara Shuzo), followed by 0.8% agarose gel electrophoresis. The fragment of about 1,200 bp was excised from the gel and purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech), and this DNA fragment was then inserted into pSTV28 (product of Takara Shuzo) at the BamHI-HindIII site. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, an expression vector, pSTVK28-hDLP1, could be obtained. A restriction enzyme map of the expression vector pSTVK28-hDLP1 is shown in FIG. 2. An Escherichia coli strain, DH5α(pSTVK28-hDLP1), was obtained by transformation with pSTVK28-hDLP1.

Example 3

Using the base sequence of the DLP1 gene of Schizosaccharomyces pombe as obtained in Example 1, homology search was conducted in a Genbank database and, as a result, a gene having 31% homology was found out by means of GENETYX (Software Development Co., Ltd.). PCR primers, mDLP1-N (SEQ ID NO:11) and mDLP1-C (SEQ ID NO:12), were prepared for obtaining that gene. Using a murine liver cDNA library (cDNA Library, Mouse Liver, plasmid type (product of Takara Shuzo)) as a template, PCR was carried out by 2 minutes of heat treatment at 94° C. followed by 35 repetitions of the following cycle: one minute at 94° C.→one minute at 56° C.→two minutes at 72° C. The thus-amplified DNA was analyzed by 0.7% agarose gel electrophoresis.

The thus-obtained fragment of about 1,200 bp was excised from the gel, purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech) and then cloned in a vector for expression in Escherichia coli using a PCR product direct cloning kit (pT7BlueT-Vector Kit, product of NOVAGEN) to give pT7-mDLP1. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, the full-length sequence occurring on the database could be obtained.

pT7-mDLP1 was cleaved with the restriction enzymes EcoRI and BamHI (products of Takara Shuzo), followed by 0.8% agarose gel electrophoresis. The fragment of about 1,200 bp was excised from the gel and purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech), and this DNA fragment was then inserted into pSTV28 (product of Takara Shuzo) at the EcoRI-BamHI site. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, an expression vector, pSTVK28-mDLP1, could be obtained. A restriction enzyme map of the expression vector pSTVK28-mDLP1 is shown in FIG. 3. An Escherichia coli strain, DH5α(pSTVK28-mDLP1), was obtained by transformation with pSTVK28-mDLP1.

Example 4

Using pKS18 (Suzuki, K., J. Biochem., 121, 496-505 (1997)) having a Schizosaccharomyces pombe cDNA-derived decaprenyl diphosphate synthase gene and primers, N-dps (SEQ ID NO:13) and C-dps (SEQ ID NO:14), PCR was carried out by 2 minutes of heat treatment at 94° C. followed by 25 repetitions of the following cycle: one minute at 94° C.→one minute at 56° C.→two minutes at 72° C. The thus-amplified DNA was analyzed by 0.7% agarose gel electrophoresis.

The thus-obtained fragment of about 1,100 bp was excised from the gel, purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech) and then inserted into the vector pBluescript II for expression in Escherichia coli at the SalI-PstI site to give an expression vector, pBSDPS. Escherichia coli DH5α was transformed with this vector to give E. coli DH5α(pBSDPS).

This transformant was further transformed with pSTVDLP1, followed by screening using 30 μg/ml chloramphenicol and 50 μg/ml ampicillin, whereby E. coli DH5α(pSTVDLP1, pBSDPS) harboring both of the vectors was obtained.

Example 5

Using the base sequence of the human decaprenyl diphosphate synthase gene appearing on a Genbank database, PCR primers, hDPS1-N (SEQ ID NO:15) and hDPS1-C (SEQ ID NO:16), were prepared. Using a human liver cDNA library (cDNA Library, Human Liver, plasmid type (product of Takara Shuzo)) as a template, PCR was carried out by 2 minutes of heat treatment at 94° C. followed by 35 repetitions of the following cycle: one minute at 94° C.→one minute at 56° C.→two minutes at 72° C. The thus-amplified DNA was analyzed by 0.7% agarose gel electrophoresis.

The thus-obtained fragment of about 1,250 bp was excised from the gel, purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech) and then cloned in a vector for expression in Escherichia coli using a PCR product direct cloning kit (pT7BlueT-Vector Kit, product of NOVAGEN) to give pT7-hDPS1. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, the full-length sequence occurring on the database could be obtained.

pT7-hDPS1 was cleaved with the restriction enzymes SalI and BamHI (products of Takara Shuzo), followed by 0.8% agarose gel electrophoresis. The fragment of about 1,250 bp was excised from the gel and purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech), and this DNA fragment was then inserted into pUC119 (product of Takara Shuzo) at the SalI-BamHI site. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, an expression vector, pUhDPS1, could be obtained. Escherichia coli DH5α was transformed with this vector to give E. coli DH5α(pUhDPS1).

Example 6

Using the base sequence of the murine solanesyl diphosphate synthase gene appearing on a Genbank database, PCR primers, mSDS-N (SEQ ID NO:17) and mSDS-C (SEQ ID NO:18), were prepared. Using a murine liver cDNA library (cDNA Library, Mouse Liver, plasmid type (product of Takara Shuzo)) as a template, PCR was carried out by 2 minutes of heat treatment at 94° C. followed by 35 repetitions of the following cycle: one minute at 94° C.→one minute at 56° C.→two minutes at 72° C. The thus-amplified DNA was analyzed by 0.7% agarose gel electrophoresis.

The thus-obtained fragment of about 1,230 bp was excised from the gel, purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech) and then cloned in a vector for expression in Escherichia coli using a PCR product direct cloning kit (pT7BlueT-Vector Kit, product of NOVAGEN) to give pT7-mSDS. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, the full-length sequence occurring on the database could be obtained.

pT7-mSDS was cleaved with the restriction enzymes EcoRI and SalI (products of Takara Shuzo), followed by 0.8% agarose gel electrophoresis. The fragment of about 1,230 bp was excised from the gel and purified using a DNA extraction kit (Sephaglas (trademark) B and Prep Kit, product of Amersham Pharmacia Biotech), and this DNA fragment was then inserted into pBluescript II SK (+) (product of Toyobo) at the EcoRI-SalI site. The DNA base sequence was determined using a DNA sequencer (model 377, product of Perkin Elmer) and a DNA sequencing kit (product of Perkin Elmer, ABI PRISM (trademark) BigDye (trademark) Terminator Cycle Sequence Ready Reaction Kit with AmpliTaq (registered trademark) DNA polymerase, FS) and conducting the reactions according to the manual attached to the kit. As a result, an expression vector, pBmSDS1, could be obtained. Escherichia coli DH5α was transformed with this vector to give E. coli DH5α(pBmSDS1).

Example 7

The transformants E. coli DH5α(pBSDPS), E. coli DH5α(pUhDPS1), and E. coli DH5α(pBmSDS1) resulting from transformation with the long-chain prenyl diphosphate synthase expression vectors constructed in Examples 4 to 6 were further transformed in various combinations with the expression vectors for activity elevatory protein expression as constructed in Examples 1 to 3.

For example, the transformant E. coli DH5α(pBSDPS) was further transformed with pSTVDLP1, as described in Example 4, to give the transformant E. coli DH5α(pSTVDLP1, pBSDPS) harboring both of the vectors. The following transformants were further obtained in the same manner:

The strain E. coli DH5α(pSTVDLP1, pUhDPS1) resulting from transformation with pSTVDLP1 and pUhDPS1;

The strain E. coli DH5α(pSTVDLP1, pBmSDS1) resulting from transformation with pSTVDLP1 and pBmSDS1;

The strain E. coli DH5α(pSTVK28-mDLP1, pUhDPS1) resulting from transformation with pSTVK28-mDLP1 and pUhDPS1;

The strain E. coli DH5α(pSTVK28-mDLP1, pBmSDS1) resulting from transformation with pSTVK28-mDLP1 and pBmSDS1;

The strain E. coli DH5α(pSTVK28-hDLP1, pUhDPS1) resulting from transformation with pSTVK28-hDLP1 and pUhDPS1; and

The strain E. coli DH5α(pSTVK28-hDLP1, pBmSDS1) resulting from transformation with pSTVK28-hDLP1 and pBmSDS1.

Among them, E. coli DH5α(pSTVDLP1, pBSDPS) has been deposited with the National Institute of Advanced Industrial Science and Technology International Patent Organism Depositary, Central 6, 1-1-1 Higashi, Tsukuba, Ibaraki, Japan as of Apr. 17, 2001 under the accession number FERM BP-7548,

E. coli DH5α(pSTVDLP1, pUhDPS1) as of Apr. 19, 2002 under the accession number FERM BP-8025,

E. coli DH5α(pSTVK28-mDLP1, pBmSDS1) as of Apr. 19, 2002 under the accession number FERM BP-8027, and

E. coli DH5α(pSTVK28-hDLP1, pUhDPS1) as of Apr. 19, 2002 under the accession number FERM BP-8026.

Example 8

The transformants E. coli DH5α(pBSDPS), E. coli DH5α(pUhDPS1) and E. coli DH5α(pBmSDS1) obtained in the above examples were each shake-cultured overnight at 37° C. in 200 ml of LB medium containing 50 μg/ml ampicillin,

E. coli DH5α(pSTVDLP1) in 200 ml of LB medium containing 30 μg/ml chloramphenicol,

E. coli DH5α(pSTVK28-hDLP1) and E. coli DH5α(pSTVK28-mDLP1) each in 200 ml of LB medium containing 50 μg/ml kanamycin,

E. coli DH5α(pSTVDLP1, pBSDPS), E. coli DH5α(pSTVDLP1, pUhDPS1) and E. coli DH5α(pSTVDLP1, pBmSDS1) each in 200 ml of LB medium containing 30 μg/ml chloramphenicol and 50 μg/ml ampicillin, E. coli DH5α(pSTVK28-hDLP1, pUhDPS1), E. coli DH5α(pSTVK28-hDLP1, pBmSDS1), E. coli DH5α(pSTVK28-mDLP1, pUhDPS1) and E. coli DH5α(pSTVK28-mDLP1, pBmSDS1) each in 200 ml of LB medium containing 50 μg/ml kanamycin and 50 μg/ml ampicillin. Bacterial cells were harvested by centrifugation (3,000 rpm, 20 minutes).

Acetone-methanol (7:2) (3 ml) was added to these cells, and extraction was effected by 6 repetitions of 30 seconds of sonication and the subsequent 30 seconds of standing on ice. Centrifugation (3,000 rpm, 5 minutes) gave an extract. This extract was vacuum-dried, 1 ml of chloroform-methanol (1:1) and an equal amount of a 0.7% aqueous solution of sodium chloride were added to the dried product, and the mixture was stirred well for attaining dissolution and then centrifuged at 14,000 rpm for 1 minute. The lower layer was extracted and dried, and the residue was dissolved in 50 μl of chloroform-methanol (2:1). This sample was spotted on a TLC plate, and developed with 100% benzene. The silica gel portion at approximately the same position as the spot obtained by development of coenzyme Q₁₀ as a standard was scraped off and extracted with 400 μl of chloroform-methanol (1:1). A 20-μl portion of this extract was analyzed by high-performance liquid chromatography (LC-10A, product of Shimadzu). For the separation, a reversed phase column (YMC-pack ODS-A, 250×4.6 mm, S-5 μm, 120A) was used, separation was effected using 100% ethanol as a mobile phase solvent, and the products coenzyme Q₉ and Q₁₀ were detected based on the absorbance at the wavelength 275 nm. The results are shown in FIGS. 4 to 8. As shown in FIGS. 4 to 8, it was revealed that the introduction of each DLP1 gene together with the prenyl diphosphate synthase gene and the subsequent expression thereof resulted in the production of coenzyme Q₉ and/or Q₁₀, which cannot be expressed in those Escherichia coli strains resulting from transformation with the prenyl diphosphate synthase gene alone.

INDUSTRIAL APPLICABILITY

The invention provides a protein involved in the expression of a eukaryotes-derived long-chain prenyl diphosphate synthase, a gene coding for such enzyme, a vector containing such enzyme gene, a transformant resulting from transformation with such vector and a long-chain prenyl diphosphate synthase gene-containing expression vector as well as a method of producing a long-chain prenyl diphosphate synthase (in particular decaprenyl diphosphate synthase and solanesyl diphosphate synthase) and of a coenzyme Q having a long-chain isoprenoid in its side chain (in particular coenzyme Q₉ or coenzyme Q₁₀). According to the invention, it is possible to produce eukaryote-derived enzymes as well as coenzyme Q₉, coenzyme Q₁₀ and the like. 

1. A transformant that is transformed with at least one selected from the group consisting of the Schizosaccharomyces pombe DPS gene, the human DPS1 gene and the mouse SDS1 gene; and a DNA defined under (a) or (b): (a) a DNA encoding a protein which has the amino acid sequence of SEQ ID NO: 2; (b) a DNA encoding a protein which has the amino acid sequence derived from the amino acid sequence of SEQ ID NO: 2 by deletion, addition, insertion or substitution of one amino acid thereof, wherein the DNA defined under (a) or (b) enables or enhances the activity of the Schizosaccharomyces pombe DPS gene, the human DPS1 gene and/or the mouse SDS1 gene in a cell of a host organism, and wherein the Schizosaccharomyces pombe DPS gene is amplifiable using polymerase chain reaction (PCR) primers of SEQ ID NOs: 13 and 14, the human DPS1 gene is amplifiable with PCR primers of SEQ ID NOs: 15 and 16, and the mouse SDS1 gene is amplifiable with PCR primers of SEQ ID NOs: 17 and
 18. 2. The transformant according to claim 1, the transformant being E. coli DH5α(pSTVDLP1, pBSDPS) (FERM BP-7548).
 3. The transformant according to claim 1, the transformant being E. coli DH5α(pSTVDLP1, pUhDPS1) (FERM BP-8025).
 4. The transformant according to claim 1, the transformant being E. coli DH5α(pSTVDLP1, pBmSDS1).
 5. A method of producing coenzyme Q, comprising: cultivating the transformant according to claim 1 in a medium to cause formation and accumulation of the coenzyme Q in the culture, and recovering the coenzyme Q from the culture, wherein a host microorganism of the transformant is capable of producing coenzyme Q. 